Coated articles are known in the art for use in window application such as insulating glass (IG) window units, vehicle windows, and/or the like. It is known that in certain instances, it is sometimes desirable to heat treat (e.g., thermally temper, heat bend and/or heat strengthen) such coated articles for purposes of tempering, bending, or the like in certain example instances. Example non-limiting low-emissivity (low-E) coatings are illustrated and/or described in U.S. Pat. Nos. 6,723,211; 6,576,349; 6,447,891; 6,461,731; 3,682,528; 5,514,476; 5,425,861; and 2003/0150711, the disclosures of which are all hereby incorporated herein by reference.
In certain situations, designers of coated articles with low-E coatings often strive for a combination of high visible transmission, substantially neutral color, low emissivity (or emittance), and low sheet resistance (Rs). High visible transmission for example may permit coated articles to be more desirable in applications such as vehicle windshields or the like, whereas low-emissivity (low-E) and low sheet resistance characteristics permit such coated articles to block significant amounts of IR radiation so as to reduce for example undesirable heating of vehicle or building interiors.
The use of oxidation graded layer(s) in low-E coatings is known. For example, see commonly owned U.S. Pat. Nos. 6,576,349 and 6,723,211, the entire disclosures of which are hereby incorporated herein by reference. The '349 patent, for example, explains that a contact layer(s) is oxidation graded so as to become less oxidized closer to an IR reflecting layer of a material such as silver. The '349 patent explains, for example, that oxidation grading of contact layer(s) is advantageous in that it permits high visible transmission to be achieved in combination with optional heat treatability.
However, the oxidation grading of a NiCrOx contact layer(s) is typically formed by sputtering. For example, more oxygen gas may be introduced via one side of a NiCr sputtering target compared to another side of the target, thereby resulting in oxidation grading of the NiCrOx layer being sputter-deposited. While this typically works very well, there are certain drawbacks. First, while sputtering a NiCr target in an oxygen inclusive atmosphere tends to cause significant amounts of chromium oxide to form in the resulting layer, the nickel does not so easily become nickel oxide (i.e., much Ni may remain in metallic form in the resulting layer). This can sometimes be undesirable in that metallic Ni tends to reduce visible transmission of the resulted coated article. Second, the use of large amounts of oxygen in a sputtering zone of a sputter coater sometimes causes undesirable target flaking to occur.
In view of the above, it will be apparent to those skilled in the art that there exists a need for a technique for forming an oxidation graded layer in a coating in a more efficient manner. In certain example instances, there exists a need for a technique for forming an oxidation graded layer in a coating in a manner which results in: (a) more oxidation of Ni if a NiCr target or the like is used in sputtering; (b) less oxygen being required in a given zone(s) or bay(s) of a sputter coater; and/or (c) reduction or elimination of the flaking effect problem.